Actually, I found merchant dispositions raised fast enough just with trading that I never tested how well gifts work. The only 'gifts' I gave merchants were the left overs when they ran out gold or useful potions (health/mana/restoration) and it wasn't worth the effort to work out some other combination of items to trade which exactly matched what they had.
Apparently having merchants identify and repair items raises they opinion, as well, but I pretty much exclusively stuck to the skills for those after the first couple levels (even then the cost was kind of steep for the start of the game, so I did just store some items to identify/repair later).
Is gifting any better than selling lots? Is there a sweet spot for gifting or selling? For instance if I sell 15 items that go for 50 gold each is that the same as 15 items at 500? Is it quantity or value that raises quicker, etc?
